THE HOUSE FLY. 21 



has been thrown onto the heap, just enough water should be added to 

 moisten it thorouglily without causing leaching. The ideal arrange- 

 ment would be to have water-tight floors in the stalls and drains 

 leading to the cistern. The liquid manure collecting in the cistern 

 could be pumped onto the manure heap, thus not only maintaining the 

 moisture content necessary to insure the greatest amount of migra- 

 tion, but also adding to the manure the valuable constituents of the 

 urine. It happens, too, that keeping the manure carefully heaped 

 and watered promotes the anaerobic fermentation and tends to pre- 

 vent to some degree the loss of ammonia and gaseous nitrogen. 



In the second place, the platform should stand not less than 1 foot 

 above the concrete floor. This is to facilitate cleaning the floor of 

 .. maggots and the debris which unavoidably accumulates there. The 

 ■j^ floor should be cleaned at least once a week, and aU liquids run into 

 the cistern in order to prevent mosquitoes from breeding in the water 

 in the floor of the trap. A thin film of oil can be used to prevent 

 mosquito breeding in the cistern. 



A third point of importance is that old manure is unfavorable 

 for fly breeding. Experiments have shown that after manure has 

 been standing on a maggot trap for 8 to 10 days it is practically free 

 from maggots, and no more will appear in it. This means that a 

 given lot of manure need remain on the maggot trap for only 10 

 days in order to prevent any breeding takmg place in it. 



The maggot trap is simple, easily constructed, and cheap. Prac- 

 tically the only cost is the initial one for construction. Very little 

 extra labor is required to operate it. Only a few minutes each day 

 are necessary to water the manure after the stable cleanings have 

 been added to the heap. Cleaning the floor to dispose of the maggots 

 and to prevent mosquito breeding will take about half an hour once 

 a week. 



That the maggot trap is effective has been shown by the junior 

 author's observations at the Maryland Agricultural CoUege. It was 

 found that the trap destroyed 99 per cent of the larvae breeding there 

 and that the number of flies at the barn and around the college 

 kitchen was reduced 67 to 76 per cent. That the reduction in the 

 prevalence of flies was not equal to the percentage of larvae de- 

 stroyed was ascribed to the fact that several other piles of untreated 

 manure were breeding out flies at near-by stables, and from these 

 places they were attracted to the bam and kitchen. 



Maggot traps may be constructed in almost any size and to suit 

 almost any conditions, and appear to be especially adapted to meet 

 the problem of fly control under rural conditions. 



